One of the new features in the elementary school mathematics curriculum is a focus on developing mental arithmetic skills for students. Based on this, elementary math textbooks include a system of exercises to strengthen students’ mental calculation abilities. To achieve this, it is essential to help students master mental arithmetic techniques and understand how to perform calculations in their heads. This article aims to identify addition and subtraction techniques within the range of 20 for second-grade students, thereby proposing some methods to enhance mental arithmetic skills, meeting the requirements of effectively implementing the elementary mathematics curriculum.One of the new features in the elementary school mathematics curriculum is a focus on developing mental arithmetic skills for students. Based on this, elementary math textbooks include a system of exercises to strengthen students’ mental calculation abilities. To achieve this, it is essential to help students master mental arithmetic techniques and understand how to perform calculations in their heads. This article aims to identify addition and subtraction techniques within the range of 20 for second-grade students, thereby proposing some methods to enhance mental arithmetic skills, meeting the requirements of effectively implementing the elementary mathematics curriculum.